1. Field of the Invention
The present invention relates to a method of and an apparatus for producing a thin metal ribbon by quenching employing a quench roll. More particularly, the present invention pertains to novel separation, guiding and transfer of the thin metal ribbon immediately after being peeled off the quench roll.
In recent years, progress has been made in production of thin metal ribbons by quenching using a quench roll. In order to carry out this process industrially, it is important to be able to wind and take up the quench-solidified thin metal ribbon into a coil at high velocity.
2. Related Applications
Applicants' assignee, Kawasaki Steel Corporation of Tokyo Japan is also the assignee of the following pending U.S. applications which relate to separation and guiding of thin strip produced by casting: U.S. Ser. No. 08/072,778, filed Jun. 7, 1993; U.S. Ser. No. 08/121,184, filed Sep. 14, 1993, and now U.S. Pat. No. 5,392,837; and U.S. Ser. No. 08/193,444 filed Feb. 8, 1994, and now U.S. Pat. No. 5,456,308.
3. Description of the Related Art
Means for guiding, conveying and taking up a thin metal ribbon can be broadly sorted into two types: namely, a first type in which a take-up reel is moved to a region in the vicinity of the quench roll so that the thin metal ribbon is attracted by and wound on the reel, and a second type in which the thin metal ribbon is conveyed and delivered to and wound on a take-up reel which is spaced apart from the quench roll.
An example of the first type is disclosed in Japanese Patent Laid-Open No. 57-95553, wherein the end of the thin metal ribbon is magnetically attracted to enable coiling.
An example of the second type is disclosed in Japanese patent Laid-Open No. 1-92716. This apparatus provides means for storage of the quench-formed thin metal ribbon, means for detecting the amount stored, and a control device for controlling the speed of the take-up roll. In one embodiment a pneumatic suction nozzle is used for conveying the thin metal ribbon to the storage section and further to the take-up reel, after the separation from the quench roll.
A ribbon take-up apparatus of the second type also is shown in Japanese patent Laid-Open No. 57-39030, wherein an air sucking roll is used.
Japanese Patent Laid-Open No. 62-45455 proposes a technique in which the thin metal ribbon is conveyed from a quench roll to a take-up reel while being clamped by clamping means such as a pair of endless belts.
Various other methods also have been proposed such as using a conveyor belt incorporating magnetic means (Japanese Patent Laid-Open No. 55-36029), employing a running ejector (Japanese Patent Laid-Open No. 62-151251), and a pair of pinch rolls carried by a conveyor truck, one of the rolls being a brush roll (Japanese Patent Laid-Open No. 3-77752).
The method disclosed in Japanese Patent Laid-Open No. 57-95553 encounters a problem in that it is not easy to magnetically attract the leading end of the thin metal ribbon without fail, because of lack of stability of the leading end of the ribbon. This instability is caused by instability of conditions such as quench roll temperature, molten metal temperature, injection pressure and operation of the injection nozzle. These are typically unstable in the period immediately after starting production.
The method disclosed in Japanese patent Laid-Open No. 1-92716 employs a pneumatic suction nozzle for conveying the thin metal ribbon separated from the quench roll to the storage section, and further to the take-up roll. In general, however, the ribbon separation point at which the thin metal ribbon leaves the quench roll is not steady and moves from time to time. In addition, the surrounding conditions are unstable immediately after the start of the operation, as described above. It is therefore difficult to catch the thin metal ribbon with the pneumatic suction nozzle. In addition, when the thin metal ribbon is wide, the ribbon tends to flutter within the guide duct and hamper stable conveyance, even if the ribbon is caught by the pneumatic suction nozzle.
The method disclosed in Japanese Patent Laid-Open No. 57-39030 also is disadvantageous in that the delivery of the thin metal ribbon from the quench roll to the take-up roll cannot be performed smoothly since the pneumatic suction roll cannot apply high enough tension to the thin metal ribbon.
The method shown in Japanese patent Laid-Open No. 62-45455 also has a drawback in that it is not easy to clamp, by means of the endless belt, the leading end of the thin metal ribbon which is being produced at a high speed. In addition, the thin metal ribbon tends to break, especially when the thin metal ribbon is wide.
The method disclosed in Japanese Patent Laid-Open No. 55-36029 employs a moving magnetic field and magnetic force for conveying the thin metal ribbon. This method meets with a problem in that it is not easy to provide a magnetic attracting force that is strong enough to ensure stable conveyance of the ribbon because of extreme thinness of the ribbon. Moreover, a repulsion force may be produced, depending on the manner of application of the magnetic force.
The technique shown in Japanese Patent Laid-Open No. 62-151251 also suffers from a disadvantage in that it is not easy to develop uniform tension in the breadthwise direction of the thin metal ribbon, so that the thin metal ribbon tends to break when the width of the ribbon is increased.
Finally, in the method disclosed in Japanese Patent Laid-Open No. 3-77752, the traction tension imparted to the thin metal ribbon tends to become non-uniform as a result of local damage or secular change in the brush pinch roll, because the traction tension is determined by the pressing force exerted by the pinch rolls and the coefficients of friction between the pinch rolls and the thin metal ribbon.